The invention relates to a gas analyzer having a respiratory tube through which the respiratory gas flows for analysis, a radiation source radiating through the respiratory tube, reflectors which direct the radiation onto radiation receiving means, and several radiation filters, each of which is assigned to a gas.
At the present time halogenated hydrocarbons in gaseous form are used routinely in mixed gases for mixed anaesthesia. Mixed anaesthesia means that sleep is induced by a hypnotic, analgesia (elimination of pain) by an analgesic and muscular relaxation by means of a muscular relaxation agent. Mixed anaesthesia is used frequently in modern hospital care. In practice, when this is carried out the patient is given a gas mixture consisting of three gases, for example oxygen, nitrous oxide, and in addition a halogenated hydrocarbon. Thus the problem arises of measuring the concentrations of the three gases.
A gas analyzer of the initially named kind is known from Canadian Pat. No. 1,000,070. A radiopaque disc with cutout portions is attached to a filter disc which is rotatable by means of a motor. The parts of the filter visible in the cutout portions are permeable with respect to various wave lengths of the received radiation. A filter is assigned to each gas concentration to be metered, which transmits those radiation components which are absorbed by the gas to be measured. The filter portions can be moved in front of a single radiation detector by means of an electric motor which rotates the disc. This gas analyzer, which is bulky and of complicated construction, can only measure different gas concentrations consecutively. Also, it has a relatively high power consumption because of the motor.